Hillforts in Scotland are earthworks, sometimes with wooden or stone enclosures, built on higher ground, which usually include a significant settlement, built within the modern boundaries of Scotland. They were first studied in the eighteenth century and the first serious field research was undertaken in the nineteenth century. In the twentieth century there were large numbers of archaeological investigations of specific sites, with an emphasis on establishing a chronology of the forts. Forts have been classified by type and their military and ritual functions have been debated.